1. Field of the Invention
The present invention relates to the field of intraocular lens and, in particular, intraocular lenses that move axially to alleviate the condition of presbyopia when implanted in the eye of a patient.
2. Description of the Art
Presbyopia is the medical term for the condition in which an individual loses the ability to focus on nearby objects such as the words in a book.
Research is currently underway to address this medical condition. In particular, research is focused on the replacement of the xe2x80x9cmalfunctioningxe2x80x9d natural lens with an artificial one that could move axially or change shape so that the patient would have restored accommodating ability.
An intraocular lens, i.e. an IOL, that moves axially when subjected to the muscular forces within the eye, will accommodate to deliver light to the proper spot on the retina. In other words, the IOL would deliver xe2x80x9cfocusablexe2x80x9d vision by axial movement.
In such an IOL it is desirable for the lens to xe2x80x9cbendxe2x80x9d at the haptic-optic junction in order to achieve the axial movement required. However, since the compression force in the eye is known to be very weak, the material strength at the haptic-optic junction must be low.
Therefore, rigid IOL materials, comprising a single material for both the optic and the haptic, like polymethylmethacrylate or PMMA, would not be suitable for providing an IOL that would accommodate as described. Also, typical xe2x80x9csoftxe2x80x9d acrylic materials, which have a tensile strength about 840 psi, may also be too strong to provide both the optic and the haptic portions of an accommodating IOL. Conversely, known xe2x80x9csoftxe2x80x9d IOL materials like silicones or acrylic hydrogels are likely too soft and, therefore, a lens made with these types of materials, as the haptics, would not function as desired. Instead, the haptics of these lenses might bend anywhere from the haptic-optic junction to the lens periphery.
Thus, it is an object of the present invention to provide an accommodating IOL which will bend at the optic-haptic junction to alleviate presbyopia or other ocular conditions wherein light is not delivered to the proper spot on the retina.
The present invention provides a method of making an intraocular lens having an optic portion joined to a haptic portion by a flexible element which comprises the steps of:
(a) forming a core of a material suitable for use as said optic portion;
(b) reacting said core to provide a first composite of said optic portion and said flexible element bonded thereto;
(c) reacting said flexible element with a material suitable for use as said haptic portion to provide a second composite; and
(d) machining said second composite to form said intraocular lens.
In one embodiment of the invention the first composite is provided by polymerizing a first polymerizable material capable of forming said flexible element to form an outer layer about said core.
In a second embodiment, the first composite is provided by reacting the core, at the surface thereof, e.g. by hydrolyzing the surface core material, to form said flexible element.
In said first embodiment, the core may be placed in a mold, said first polymerizable material may be placed in said mold about said core and said first polymerizable material may be polymerized around said core.
In either embodiment, a second polymerizable material, capable of forming said haptic portion, is polymerized about said first composite to form an outer layer about said first composite.
The second composite is preferably provided by positioning said first composite in a mold, placing a second polymerizable material in said mold about said first composite and polymerizing said second polymerizable material.